Previous work in our group resulted in the discovery, isolation, and characterization of several secretory proteins specific for different segments of the male reproductive system, and believed to be important in the attainment of full maturation and motility of sperm. Three of these proteins, testicular androgen binding protein (ABP), acidic epididymal glycoprotein (AEG), and a prostatic steroid binding protein, prostatein, will be studied in detail relying on specific antisera developed in our laboratories against highly purified antigens isolated from rat tissues. The proteins will be localized in tissue sections with both light and electron microscopic immunocytochemistry (ICC). In addition, radioimmunoassays (RIA) will be developed for quantitative estimation of the tissue contents and blood levels of all three proteins. Both ICC and RIA techniques will be used to study the cellular and subcellular distribution, the secretory mechanisms, ontogeny, hormonal regulation, fate in the male reproductive tract, and possible artificial control of secretion of these organ-specific, androgen dependent proteins secreted in the male reproductive tract. These studies will provide, for the first time, specific insights into the protein secretory mechanisms in the male reproductive system, and may offer novel possibilities for the artificial control of male fertility.